1. Field of the Invention
This invention relates to improvements in the production of hexagonal plate crystals of aluminum sulfate from chemically impure aluminum sulfate solutions.
2. Description of the Prior Art
Glue-like, fibrous, and in some instances, flake crystals of aluminum sulfate can be obtained by treating minerals containing alumina with sulfuric acid, extracting aluminum salts from the mineral and crystallizing aluminum sulfate from the extracted solution. Crystalline aluminum sulfate can also be obtained together with iron sulfate from waste sulfuric acid or the like which contains considerable amounts of iron and aluminum. However, aluminum sulfate crystals cannot be separated easily from crystals of the other materials in these processes.
Heretofore, chemically pure aluminum sulfate crystals have been generally obtained by crystallizing the impure aluminum salts from previously purified aluminum sulfate solutions. However, these purification procedures have been troublesome and it has been difficult to obtain chemically pure aluminum sulfate crystals inexpensively by those prior art techniques. A need, therefore, continues to exist for a simple, low-cost method of obtaining pure, crystalline aluminum sulfate.